A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its center and perpendicular to its plane with an angular velocity ω. Another disc of the same dimensions but of mass 14M is placed gently on the first disc co-axially. The angular velocity of the system will be:

1.  23ω

2.  45ω

3.  34ω

4.  13ω

Subtopic:  Angular Momentum |
 81%
From NCERT
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When a torque acting upon a system is zero, then which of the following will be constant 

1.  force

2.  Linear momentum

3.  Angular momentum

4.  Linear impulse

Subtopic:  Angular Momentum |
 86%
From NCERT
PMT - 1997
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Consider a system of two particles having masses m1 and m2. If the particle of mass m1 is pushed towards the center of mass of particles through a distance, by what distance would be the particle of the mass m2 move so as to keep the center of mass of particles at the original position?

1.  m1m1 + m2d

2.  m1m2d

3.  d

4.  m2m1d

Subtopic:  Center of Mass |
 55%
From NCERT
PMT - 2004
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A flywheel is in the form of a uniform circular disc of radius 1 m and mass 2 kg. The work which must be done on it to increase its frequency of rotation from 5 rev s-1 to 10 rev s-1 is approximately

1.  1.5 x 102 J

2.  3.0 x 102 J

3.  1.5 x 103 J

4.  3.0 x 103 J

Subtopic:  Rotational Motion: Kinematics |
 58%
From NCERT
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A constant torque acting on a uniform circular wheel changes its angular momentum from A0 to 4 A0 in 4s. The magnitude of this torque is 

1. 3A04

2. 4 A0

3. A0

4. 12 A0

Subtopic:  Angular Momentum |
 88%
From NCERT
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Two discs are rotating about their axes, normal to the discs and passing through the centres of the discs. Disc D1 has 2 kg mass and 0.2 m radius and initial angular velocity of 50 rad s-1. Disc D2 has 4 kg mass, 0.1 m radius and initial angular velocity of 200 rad s-1. The two discs are brought in contact face to face, with their axes of rotation coincident. The final angular velocity (in rad.s-1) of the system is

1. 60

2. 100

3. 120

4. 40

Subtopic:  Angular Momentum |
 73%
From NCERT
NEET - 2013
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A body rolls down an inclined plane without slipping. The fraction of total energy associated with its rotation will be

1. K2+ R2
2. K2R2
3. K2K2+ R2
4. R2K2+ R2

Where k is radius of gyration of the body about an axis passing through centre of mass and R is the radius of the body. 

Subtopic:  Rolling Motion (OLD NCERT) |
 74%
From NCERT
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In the following figure, a weight W is attached to a string wrapped round a solid cylinder of mass M mounted on a frictionless horizontal axle at O.

If the weight starts from rest and falls a distance h, then its speed at that instant is

1. Proportional to R

2. Proportional to 1R

3. Proportional to 1R2

4. Independent of R

Subtopic:  Torque |
 55%
From NCERT
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A solid cylinder rolls down an inclined plane that has friction sufficient to prevent sliding. The ratio of rotational energy to total kinetic energy is

1.  12

2.  13

3.  23

4.  34

 

Subtopic:  Rolling Motion (OLD NCERT) |
 70%
From NCERT
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A swimmer while jumping into water from a height easily forms a loop in the air, if

1. He pulls his arms and legs in

2. He spreads his arms and legs

3. He keeps himself straight

4. None of the above

Subtopic:  Moment of Inertia |
 78%
From NCERT
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